The purpose of this three-part project is to examine the input-output organization of neurons in the motor cortex. Rats have been chosen as the primary experimental animal since they are readily available, easy to condition, and have small, lissencephalic brains. (1) Neuroanatomical and neurophysiological techniques are being employed to characterize the first motor cortex (MI) in rats and determine the connectional relationships of MI with other neural structures. (2) We are planning to record neuronal activity from several classes of projection neurons in the forelimb area of MI cortex in awake, behaving rats. In these experiments, the relationship of the neuronal activity to motor output will be examined for each type of neuron, e.g. corticospinal and corticorubral cells. (3) We are combining intracellular recording with intracellular injection of a tracer, horseradish peroxidase, to visualize the intracortical distribution of neuronal processes belonging to identified projection neurons.